Method of making oil gas interchangeable with natural gas



Feb. 14., 1956 E. s. PETTYJOHN ET AL 2,734,810

METHOD OF MAKING OIL GAS INTERCHANGEABLE WITH NATURAL GAS Filed March11, 1952 2 Sheets-Sheet 1 14, 1956 E. s. PETTYJOHN ET AL 2,734,810

METHOD OF MAKING OIL GAS INTERCHANGEABLE WITH NATURAL GAS Filed March11, 1952 2 sh9ebSShe6t 2 (/39 $772202? -\Z4U $227 72? index /230 Z417142222.262

- 2 6%, wzmm rm United States Patent METHOD OF MAKING 01L GASINTERCHANGE- ABLE WITH NATURAL GAS Elmore S. Pettyjohn, Evanston, andHenry R. Linden, Franklin Park, 111., and Wiliiarn L. Lee, Atlanta, Ga,assignors to Institute of Gas Technology, Chicago, 111., a corporationof Illinois Application March 11, 1952, Serial No. 275,952 4 Claims.(Cl. 48-211) This invention relates to a method of preparing an oil gasby cracking petroleum oils, particularly under conditions producingcarbon deposits in amounts preventing continuous cracking due to thenecessity for frequent removal of carbon deposits.

An imporatnt object of the invention is to provide a method of thenature indicated which can be carried out, if desired, in conventionalregenerative apparatus for making oil gas with only slight modificationof such apparatus, and which is eliective to make oil gas under lesssevere cracking conditions and at a faster rate and to make an oil gasmore interchangeable with natural gas, all as compared with conventionalregenerative methods for making oil gas.

Other and further objects and features of the present invention willbecome apparent from the following description and appended claims asillustrated by the accompanying drawings showing, diagrammatically andby way of examples, apparatus for carrying out the meth- (ads of thepresent invention. More particularly:

Fig. l is a vertical, longitudinal, sectional view (with parts shown inelevation) of an apparatus according to the present invention for makingoil gas;

Fig. 2 is a fragmentary view of the main gas duct of the apparatus ofFig. 1 as modified in accordance with the disclosure in the copendingapplication of Elmore S. Pettyjohn entitled Oil Gas Plant, Serial No.270,956 filed on February 11, 1952, now abandoned;

Fig. 3 is a vertical, longitudinal, sectional view (with parts shown inelevation) of another apparatus according to the present invention formaking oil gas; and

Fig. 4 is a fragmentary view of the main gas duct of the apparatus ofFig. 3 as modified in accordance with the disclosure in the above-notedcopending application of Elmore S. Pettyjohn.

Referring now to Fig. 1, the apparatus there shown includes twogenerators 1t) and 12 disposed adjacently each other and twosuperheaters 14 and 16, disposed, respectively, adjacently the generatorand the generator 12. At their bottoms, the generator 10 and thesuperheater 14 are interconnected by a duct 18 to form a firstgenerator-superheater pair, while the generator 12 and the superheater16 are similarly interconnected by a conduit 20 to form a secondgenerator-superheater pair. The generators 10 and 12 and thesuperheaters 14 and 16 are provided with interior checker brick work 22made up of layers of closely spaced bricks arranged in closelyoverlapping position (as between the various layers) so as to provide amaximum number of tortous gas passages whereby highly etficient heatexchange is promoted between the gas and the brick work. Due to theoverlapping of the checker bricks, each brick structure forms a unifiedmass perforated by a large number of gas passages, with the result thatthe temperature therein will be substantailly uniform. The crackingeffected within each brick structure will therefore be uniformthroughout each brick work.

The roofs of the generators 10 and 12 are each arched 2,734,810 PatentedFeb. 14, 1956 above the brick work therein and are each formed,respectively, with central, vertical apertures 24 and 26 reccivingvertical ducts 28 and 30 opening upwardly into a crossover duct 32. Theroofs of the superheaters 14 and 16 are likewise arched above the brickwork therein and are each formed, respectively, with central, verticalapertures 34 and 36 receiving vertical ducts 38 and 40 having upperopenings closed by valves 42 and 44. Stacks 46 are provided above theupper ends of the ducts 38 and 40 to receive gases vented therefrom whenthe valves 42 and 44 are opened.

An air duct 48 having a valve 50 discharges into the duct 28 leadinginto the generator 10 and another air duct 52 having a valve 54discharges air into the duct 30 leading into the generator 12. An oilspray device 56 for the generator 10 extends through the duct 28 and issupplied with oil to be cracked through a pipe 58 having a valve 60 andwith oil to be burned for heating through a pipe 62 having a valve 64.An oil spray device 66 for the generator 12 extends through the duct 30and is supplied with oil to be burned for heating through a pipe 68having a valve 70 and with oil to be cracked through a pipe 72 having avalve 74.

A gas duct 76 branches 011 from the duct 38 of the superheater 14 andhas connected thereto an air duct 78 valved at 80 as well as a steampipe 82 valved at 84. Similarly, a gas duct 86 branches off from theduct 70 of the superheater 16 and has connected thereto an air duct 88valved at 90 aswell as a steam pipe 92 valved at 94. Both ducts 76v and86 discharge into a main gas duct 96 leading to a wash box 98 containingliquid 1% into which the lower end of the main gas duct 96 dips. Anothergas duct 102 conducts the make gas from the wash box 98. A valve 104 inthe top of the duct 96 serves alternately to close the orifices of theducts 76 and 86 into the duct 96.

As so far described, the apparatus of Fig. l is conventional. Accordingto the present invention, a pipe valved at 112 extends through the duct38 and another pipe 114 valved at 116 extends through the duct 40. Thepipes 110 and 114 serve to admit, respectively, into the superheaters 14and 16 liquid or vaporized propane, butane, gasoline, light naphtha, ora mixture thereof.

In the operation of the apparatus of Fig. 1 through a four-stage cycle,a first blast period is initiated by closing the valve 42, then openingthe valve 44, and moving the valve 104 to close the outlet of the duct76. Primary air is admitted through the conduit 78 by opening the valve81;. Secondary air is admitted through the conduit 52 by opening itsvalve 54 and oil for heating is supplied through the pipe 68 by openingits valve 70. ,The primary air passes through the superheater 14 and thegenerator 10 wherein cracking has been effected in the preceding makestage, and the air then removes carbon deposited in the brick work ofthis first generator-superheater pair while being preheated beforereaching the second generatorsuperheater pair. At the 'end of this blastperiod, the valves 54, 7t), 80, and 44 are closed. The apparatus may bepurged by briefly opening the valve 84 of the steam pipe 82 before thevalve 44 is closed.

In the next succeeding make period, oil is cracked in the secondgenerator-superheater pair. For this purpose, the valve 112 of the pipe110 is opened to supply a light hydrocarbon of the nature indicated andthe valve 74 of the pipe 72 is opened to supply oil to the generator 12.The make gas leaves the top of the superheater 16 and passes through theducts 86 and 96, through the wash box 98 and into the gas main 102.Duringthis period, carbon is deposited in the brick work of the secondgenerator-superheater pair. At the conclusion of this make period, thevalves 74 and 112 are closed and the valve 104 is moved to close theoutlet of the duct 86 into the duct 96 and to open the outlet of theduct 76.

In the next succeeding blast period, the valve 42 is opened and thevalve 94 of the steam pipe 92 may then be opened briefly to purge theapparatus. Primary air is admitted through the pipe 88 by opening thevalve 90 to remove the carbon deposits from the brick work in thegenerator 12 and superheater 16, the air being preheated while passingtherethrough. Secondary air is admitted from the pipe 48 by opening itsvalve 50 and oil is supplied from the pipe 62 by opening the valve 64.At the end of the blast period, the valves 64, 90, 50, and 42 areclosed. Before the valve 90 is closed, the valve 94 of the steam pipe 92may be opened briefly to purge the apparatus.

In the next succeeding make period, the valve 116 of the pipe 114 isopened to supply a light hydrocarbon of the nature indicated and oil issupplied to the generator by opening the valve 60 in the oil pipe 58.The make gas leaves the top of the superheater 14 and passes through theducts 76 and 96, through the wash box 98 and into the gas main 102.During this period, carbon is deposited in the brick work in the firstgenerator-superheater pair. At the conclusion of this make period,valves 60 and 116 are closed and the valve 104 is moved to close theoutlet of the duct 76 into the duct 96 and to open the outlet of theduct 86. The valve 94 is then opened, and the valve 84 of the steam pipe82 may be opened briefly to purge the apparatus. The apparatus is thenready for a repetition of the four-stage cyclic regenerative processabove described.

By way of a modified method of operating the apparatus of Figure 1, oilto be cracked while a light hydrocarbon is fed into the apparatusthrough the pipe 110 may be supplied through either the pipe 58 or thepipe 114 instead of the pipe 72. Or, oil to be cracked while a lighthydrocarbon is fed into the apparatus through the pipe 114 may besupplied through either the pipe 72 or the pipe 110 instead of the pipe58.

In the above-described process, a light hydrocarbon (of the naturepreviously indicated) is cracked in the superheater of onesuperheater-generator pair while a heavy oil is cracked in the generatorof the other set. The product gas from the light hydrocarbons cracked inthe superheater flows into the generator, so that the heavy oil iscracked in an atmosphere of this product gas produced from theabove-disclosed light hydrocarbons. As a result, the make gas producedis more completely interchangeable with natural gas. Further, both thegenerator and the superheater are simultaneously utilized to producegas, so that the rate of gas production is greatly increased as comparedwith that possible in conventional regenerative apparatus for making oilgas of high heating value when operated according to conventionalmethods. Finally, the heat normally used for superheating the I steamconventionally introduced into the apparatus during admission of oil tobe cracked is utilized for cracking the indicated light hydrocarbons sothat the generation of oil gas is effected with a much smaller fuelconsumption per unit of oil gas made than has heretofore been foundpossible. Only slightly more tar is formed than if the oil had beencracked in the absence of the indicated light hydrocarbons.

A regenerative apparatus of somewhat different design from that shown inFig. l is illustrated in Fig. 3. The apparatus of the last-mentionedfigure is generally U- shaped, having left and right shells indicatedgenerally respectively, at 150 and 152 and interconnected at theirbottoms by a conduit 154. The left shell 150 has provided therein spacedlower and upper checker brick works 156 and 158 functioning similarly,respectively, to the generators and superheaters of the apparatus ofFig. l. The right shell 152 is provided with similarly functioningspaced lower and upper checker brick works 160 and 162. An oil spraydevice 164 projecting into the Cir interspace between the generator 156and the superheater 158 is supplied with oil to be cracked through apipe 166 valved at 168 and with oil to be burned for heating through apipe 170 valved at 172. An air duct 174 valved at 176 also projects intothe said interspace. Similarly, an oil spray device 178 projecting intothe interspace between the generator 160 and the superheater 162 issupplied with oil to be cracked by a pipe 180 valved at 182 and with oilto be burned for heating through a pipe 184 valved at 186. An air duct188 valved at 190 also projccts into the interspace between thegenerator 160 and the superheater 162.

The roof of the shell is arched above the brick work 158 and is formedwith a vertical aperture 192 receiving a vertical duct 194 closedupwardly by a valve 196 which when opened permits venting of the shell150 into a stack 198. Similarly, the shell 152 is arched above the brick162 and is formed with a vertical aperture 200 receiving a vertical duct202 closed upwardly by a valve 204 which when opened permits venting ofthe shell 152 into a stack 206. A gas duct 208 branches off from theduct 194 for the shell 150 and has an air duct 210 valved at 212 as Wellas a steam pipe 214 valved at 216 connected thereto. Similarly, a gasduct 220 branches off from the duct 202 for the shell 152 and-has an airduct 222 valved at 224 as well as a steam pipe 226 valved at 228connected thereto. Both ducts 194 and 202 discharge into a gas duct 230having a lower end dipping into liquid 232 in a wash box 234 from whichmake gas is discharged into a gas main 236. A valve 238 at the top ofthe gas duct 230 is movable between extreme positions closing theoutlets into the gas duct 230, respectively, of the ducts 208 and 220.

As so far described, the apparatus of Fig. 3 is conventional.

According to the present invention, a pipe 250 valved at 252 extendsthrough the duct 194 and another pipe 254 valved at 256 extends throughthe duct 202. The pipes 250 and 254 serve to admit, respectively, intothe superheaters 158 and 162 liquid or vaporized propane, butane,gasoline, light naphtha, or a mixture thereof.

In the operation of the apparatus of Fig. 3, blasting is first carriedout. The valve 196 is closed, the valve 204 is opened, and the valve 238is moved to close the outlet of the duct 208. Primary air is admittedfrom the duct 210 by opening the valve 212 to remove anycarbon deposits(formed in a preceding cracking or make period) in the superheater 158and the generator 156, the primary air then being preheated on passagethrough these structures. Secondary air is admitted through the duct 188by opening its valve 190, and oil for burning is supplied by opening thevalve 186 of the pipe 184. The generator and the superheater 162 arethus brought to cracking temperatures. At the end of the blast period,the valves 186, 190, 212, and 204 are closed. Before the valve purged byopening the steam valve 216 briefly.

In the next succeeding make period, the valve 182 of the oil pipe isopened, as is also the valve 252 of the pipe 250. The make gas leavesthe shell 152 through the duct 202 and passes through the ducts 220 and230 and through the wash box 234 into the gas main 236. Carbon isdeposited in the generator 160 and the superheater 162. At the end ofthe make period, the valves 182 and 252 are closed and the valve 238 ismoved so as to close the outlet of the duct 220.

In the next succeeding blast period, the valve 196 is opened and theapparatus may then be purged by briefly opening the valve 228 of thesteam pipe 226. Primary air is admitted from the duct 222 by opening thevalve 224, to remove carbon deposited in the generator 160 and thesuperheater 162, this air being preheated on passing through the brickwork of the structures. Secondary air is admitted from the conduit 174by opening the valve 176 and oil is supplied to the spray device 164from the 204 is closed, the apparatus maybe i pipe 170 by opening thevalve 172. At the end of this blast period, the valves 172, 224, 176,and 196 are closed. Before the valve 196 is closed, the apparatus may bepurged by briefly opening the valve 228 of the steam pipe 226.

In the next succeeding make period, the valve 168 of the oil pipe 166and the valve 256 of the pipe 254 are opened. The make gas leaves thetop of the shell 150 and passes through the ducts 194, 208, and 230 andthrough the wash box 234 into the gas main 236. Carbon is deposited inthe generator 156 and the superheater 158. At the conclusion of thismake period, the valves 168 and 256 are closed, and the valve 238 ismoved so as to close the outlet of the duct 208. The valve 204 isopened, and the apparatus may then be purged by briefly opening thevalve 216 of the steam pipe 214, to make the apparatus ready for arepetition of the above-described four-stage cyclic operation.

Apart from the stages hereinabove described, the apparatus of Fig. 3 isoperated exactly as the apparatus of Fig. 1 to produce a make gassimilar to that formed in the apparatus of Fig. 1.

In the two make periods, the oil to be cracked need not be introducedthrough the pipe 130 when a light hydrocarbon is admitted through thepipe 250 but can instead be introduced through the pipe 166, or throughboth pipes 180 and 166. When a light hydrocarbon is admitted through thepipe 254, oil to be cracked can be introduced through either of thepipes 166 or 180, or through both of these pipes.

By way of an example, we tabulate hereinbelow the results obtained byoperating an apparatus such as that shown in Fig. 3 for cracking BunkerC oil at an average temperature of from 1450 to 1470 F. in an atmosphereprovided by admitting propane to the superheaters. The oil was fed intothe apparatus at the rate of 85 gallons per run and the propane (inliquid form) at the rate of 20 gallons per run. There were 12 runs perhour producing make gas at the rate of 116,600 s. c. f./hour. The makegas analysis is tabulated as follows:

The above gas is more interchangeable with natural gas than conventionalhigh heating value oil gas. The concentration of diluents (CO2, 02 andN2) can be adjusted to a more desirable mixed heating value and specificgravity by reducing the volume of combustion gas permitted to enter theproduct gas. The make gas rate when feeding only the 85 gallons ofBunker C fuel oil per run was reduced to 97,000 s. c. f./hour, 75 lbs.per minute of make steam then being used as compared to the 45 lbs. ofmake steam per minute used when propane was cracked simultaneously withthe oil. More than 20 gallons of propane per run can be admitted intothe apparatus, with resultant formation of more than 116,600 s. c.f./hour of make gas.

In general, the same type of oil gas can be produced by proceeding asfollows. The cracking of the aboveindicated light hydrocarbon in thesuperheaters is carried out at a temperature range from 1200 to 1650 F.and at a residence time of from to 12 seconds. One part of the indicatedlight hydrocarbons may be cracked in the superheater for each 2 to 10parts of oil cracked in the generator. The oil referred to hereinaboveas being cracked in the generators includes fuel and gas oils, and thevarious heavy petroleum oils such as heavy gas oil and Bunker C oil.Ordinarily, heavy petroleum oils are employed. The average crackingtemperature ranges from 1350 to 1700 F., and the residence time from 1to 5 seconds. The cracking temperatures and residence time aremaintained in the same manner as in the operation of a conventionalregenerative apparatus for making (at atmospheric pressure) an oil gashaving a heating value of from 700 to- 1500 and preferably of from 950to 1200 B. t. u./s. c. f.

it should be noted that in the operation (at atmospheric pressure) of aconventional regenerative apparatus for making oil gas having a heatingvalue of from 700 to 1500 B. t. u./s. c. f. (at a cracking temperatureof from 1350 to 1700 F., at a residence time of from i to 5 seconds, andat a partial pressure of the oil gas during cracking ranging from 0.3 to0.4 atmosphere), the composition of the gas formed is fixed by thediluent (combustion blast or purge gas) free heating value thereof,being independent of the nature of the oil being cracked. The relationbetween the gas composition and the heating value of the diluent freeoil gas is tabulated as follows:

Paralfins Ethylene Higher illuminants Hydrogen i- HMA Gasman Inproceeding according to the present invention, the cracking of the. oilin the generators is carried out within the indicated ranges oftemperature and residence time. Within these ranges, the conditions areadjusted to give a make gas of the particular heating value desired, dueregard being had for the fact that the cracking in the super-heaters ofthe indicated light hydrocarbons reduces the diluent content of the makegas in proportion to the quantity of light hydrocarbons cracked,correspondinglyreduces the specific gravity of the make gas, raises theparaflin content of the make gas and reduces the make. contents ofolefins and other illuminants all as com pared with the make gas of thesame heating value obtained in the conventional regenerative apparatusfor making oil gas. The net effect is one equivalent to making a finaloil gas of reduced diluent-free heating value without increasing theseverity of cracking and thereby avoiding increased carbon formation andtar viscosity.

The composition of the oil gas produced according to the presentinvention is such as to make the oil gas more completely interchangeablewith natural gas than the oil gas produced by conventional crackingmethods at the same conditions of cracking severity. For a completediscussion of the interchangeability of high heating value oil gas andnatural gas, reference is made to the copending application of Elmore S.Pettyjohn and Henry R. Linden entitled Fuel Gas Interchangeable withNatural Gas and Method of Preparing the Same, Serial No. 270,957, filedon February 11, 1952.

It is believed that the higher paraffin to. olefin ratio obtained in themake. gas prepared according to the present invention is in part due tothe relatively increased oil gas partial pressure obtained by crackingthe oil in an atmosphere of product gas (obtained by cracking theindicated light hydrocarbons in the superheaters) rather than bycracking the oil in a steam atmosphere, as is conventionally done inoperating regenerative apparatus for making oil gas.

A still higher paraflin to olefin ratio and a higher paraffin tohydrogen ratio in the make gas (with consequently more completeinterchangeability of the make gas with natural gas) can be secured bycarrying out the make steps of the above process under superatrnosphericpressure. For this purpose, the apparatus of Fig. 1 may be modified asillustrated in Fig. 2. As there shown, the duct 96 is constricteddownstream of the valve 104, as indicated at 106. This constriction isdimensioned so as to dam up the oil gas pressure generated within theapparatus when oil is cracked therein. Further, the conduit 96 is madesufiiciently wide downstream of the constriction 106 to permit expansionof oil gas passing therethrough whereby normal functioning of the washbox 98 is made possible. The modified apparatus of Fig. 2 is operatedexactly as the apparatus of Fig. 1, but in the apparatus of Fig. 2 thecracking steps of the cycle are carried out under superatrnosphericpressure (which is not true of the blasting steps), with resultantfurther irnprovement in the itnerchangeability of the make gas withnatural gas, as noted hereinabove. For further details, reference ismade to the copending application of Elmore S. Pettyjohn entitled OilGas Plant.

By way of a modification of the apparatus of Fig. 3, the duct 230 may beconstricted downstream of the valve 238, as shown at 240 in Fig. 4. Thisconstriction is dimensioned so as to dam up the pressure of the oil gasgenerated in the apparatus when oil is cracked therein. The pressureupstream of the constriction 240 does not interfere with a normaloperation of the wash box 234, for the gas issuing from the constrictionexpands downstream of the constriction before entering the wash box 234.The improved results obtained by cracking under pressure are discussedabove in connection with the description of Fig. 2.

Many details of construction and procedure may be variedwithoutdeparting from the principles of this invention, and it is, therefore,not our intention to limit the patent granted on this inventionotherwise than necessitated by the scope of the appended claims.

We claim:

1. A cyclic regenerative oil cracking process for making an oil gas forsupplementing natural gas which comprises providing a first and a secondgenerator and a first and a second superheater each capable of absorbingheat and of releasing heat on gas flow therethrough, heating saidgenerators and superheaters to a cracking temperature of 1350 to 1700F., thereafter flowing through said second superheater, secondgenerator, first generator and first superheater in said sequence a.hydrocarbon selected from the group consisting of propane, butane,gasoline, light naphtha and mixtures thereof to crack said hydrocarbonwhile simultaneously flowing a petroleum oil through said firstgenerator and said first superheater in said sequence at a rate which isequivalent to a residence time of from 1 to 5 seconds, whereby said oilis cracked in the presence of the cracking products of said hydrocarbonand in the absence of steam to form oil gas, cooling said oil gas thusformed, thereafter flowing air through said first superheater, firstgenerator, second generator and second superheater in said sequence toremove carbon deposited in said first generator and said firstsuperheater when said oil is cracked therein, while flowing additionalair through said second generator and said second superheater 1n saidsequence and flowing oil into said second generator for combustiontherein, said flowing of air and oil being continued until said bodieshave been raised to the cracking temperature indicated and the hotcombustion product gases being vented after flowing out of said secondsuperheater, thereafter flowing said hydrocarbon through said firstsuperheater, first generator, second generator and second superheater insaid sequence to crack said hydrocarbon, while simultaneously flowingsaid oil through said second generator and second superheater in saidsequence at a rate which is equivalent to a residence time of 1 to 5seconds, whereby said oil is cracked in the presence of the crackingproducts of said hydrocarbon and in the absence of steam to form oilgas, cooling the oil gas thus formed, thereafter flowing air throughsaid second superheater, second generator, first geenrator and firstsuperheater in said sequence to remove carbon deposited in said secondsuperheater and said second generator when said oil is cracked therein,while simultaneously flowing additional air through said first generatorand first superheater in said sequence and flowing oil into said firstgenerator for combustion therein, said flow of said air and oil beingcontinued until said generators and superheaters have been raised to acracking temperature of 1350 to 1700 F. and the hot combustion productgases being vented after flowing out of said second superheater, andthereafter repeating the cycle recited hereinabove beginning with thefirst recited flowing of said hydrocarbon and said oil.

2. A method according to claim 1 in which said pe-' troleum oil iscaused to flow through said second generator, first generator, and firstsuperheater in said sequence while said hydrocarbon is caused to flowthrough said second superheater, second generator, first generator andfirst superheater in said sequence, said petroleum oil also being causedto flow through said first generator, second generator and secondsuperheater in said sequence while said hydrocarbon is caused to fiowthrough said first superheater, first generator, second generator, andsecond superheater in said sequence. I V

3. A method of making an oil gas interchangeable with natural gas whichcomprises passing a hydrocarbon selected from the group consisting ofpropane, butane, gasoline, light naphtha and mixtures thereof through aheated vessel at a temperature of 1200 to 1600 F. and for a residencetime of 10 to 12 seconds to crack said hydrocarbon, immediately passingsaid hot cracking products into a reactor while simultaneouslyintroducing into the reactor a normally liquid petroleum fraction tocrack said fraction in the presence of said hot cracking products and inthe absence of steam, the cracking of said fraction being carried out ata temperature of 1350 to 1700 degrees Fahrenheit and at a residence timeof from 1 to 5 seconds to obtain a gas containing a major proportion ofparafiinic hydrocarbons.

4. The method of claim 3 wherein two to ten parts of said liquidpetroleum fraction are employed for one part of said hydrocarbon.

References Cited in the file of this patent UNITED STATES PATENTS543,992 Kirkham Aug. 6, 1895 982,754 Waring Jan. 24, 1911- l,97l,729Perry Aug. 28, 1934 2,192,815 Johnson et al Mar. 5, 1940 2,580,766 HallJan. 1, 1952 2,592,591 Odell Apr. 15, 1952 2,605,176 Pearson July 29,1952 2,656,307 Findlay Oct. 20, 1953

3. A METHOD OF MAKING AN OIL GAS INTERCHANGEABLE WITH NATURAL GAS WHICHCOMPRISES PASSING A HYDROCARBON SELECTED FROM THE GROUP CONSISTING OFPROPANE, BUTANE, GASOLINE, LIGHT NAPHTHA AND MIXTURES THEREOF. THROUGH AHEATED VESSEL AT A TEMPERATURE OF 1200 TO 1600 * F. AND FOR A RESIDENCETIME OF 10 TO 12 SECONDS TO CRACK SAID HYDROCARBON, IMMEDIATELY PASSINGSAID HOT CRACKING PRODUCTS INTO A REACTOR WHILE SIMULTANEOUSLYINTRODUCING INTO THE REACTOR A NORMALLY LIQUID PETROLEUM FRACTION TOCRACK SAID FRACTION IN THE PRESENCE OF SAID HOT CRACKING PRODUCTS AND INTHE ABSENCE OF STEAM, THE CRACKING OF SAID FRACTION BEING CARRIED OUT ATA TEMPERATURE OF 1350 TO 1700 DEGREES FAHRENHEIT AND AT A RESIDENCE TIMEOF FROM 1 TO 5 SECONDS TO OBTAIN A GAS CONTAINING A MAJOR PROPORTION OFPARAFFINIC HYDROCARBONS.